This invention relates to a novel synthetic aluminosilicate zeolite and a method of preparing such a zeolite material. The present invention is also directed to a process for the production of lower olefins from methanol and/or dimethyl ether with the use of such a zeolite material as catalyst.
It is known in the art that hydrocarbons can be produced by catalytic conversion of methanol and/or dimethyl ether. It is also known that zeolite materials can be used for this purpose as catalyst. Crystalline aluminosilicate zeolite materials, which are known as molecular sieves, are made up of an anionic three-dimensional framework of SiO.sub.4 and AlO.sub.4 cross-linked by the sharing of oxygen atoms, the anionic charge being balanced by the inclusion in the crystal of an exchangeable cation such as an alkali metal cation. Typical of such synthetic crystalline zeolites are "ZSM-5" and "ZSM-34" produced by Mobil Oil Corp. (See, for example, U.S. Pat. No. 3,702,886). Although "ZSM-5" is effective in producing hydrocarbons of up to 10 carbon atoms (gasoline fraction) by conversion of methanol, it is not suited for the conversion of methanol into lower olefins such as ethylene and propylene. "ZSM-34", on the other hand, exhibits a high selectivity to lower olefins. However, it suffers from a drawback that the catalyst life is very short.